Then I will offer a suggestion to help alleviate the button problem. It's one I've used on the Kindle here. (Yea, that bar/button/handrest seems badly designed for long reading.)
Just shove a thin strip of closed cell foam under the edge where your hand normally lays. You might have to look around to find some but it shouldn't be to hard to find. The extra resistance at the point of holding is usually enough to prevent it from accidentally tripping quite so often.
For those who don't know, there are a couple different foams out there you can get a hold of. One is the big and fluffy one used in cheap cushions and pillows (generally called "open cell".) The other is a denser and heavier material ("closed cell") usually found in sheet formats only and used for things like tray liners for precision measuring devices or gasket material. I found the best places to find it for most people is large hardware stores and auto supply houses.
NOTE: "Closed cell" foam is NOT the same as rubber! Rubber is...well, rubber. Rubber bends and stretches but really doesn't compact. "Closed cell" will bend like rubber but also has some slight compact ability so placing a thin strip between the bar and the reader basically just makes it a stiffer button.
NOTE DUO: Don't try and shove it all the way under the bar, just a little under the edge. Putting it to far under the edge will just place unneeded strain on the bar as well as make it ridiculously hard to press after time passes.
And personal note: (/whine)I still wish they would just change out the screen on a 1150 to eink and keep the basic form factor and screen flip button. I have yet to find ANY reader that suited my long term reading comfort as well as that did.(/whine)